Japanese Language Stack Exchange is a question and answer site for students, teachers, and linguists wanting to discuss the finer points of the Japanese language. It's 100% free, no registration required.

They should be from different verbs. 行ける > いけない and 行く > いかない. But I'm not familiar with 行ける at all so I can't say for sure what the difference is.
–
FlawNov 21 '11 at 2:21

Alternatively they can be from the same verb. 行く +(short potential form) to get 行ける and then +negative to get いけない. This would mean "Cannot go". Compare with 行かない which means "will/does not go".
–
FlawNov 21 '11 at 2:33

@yadokari yeah, that's where I realized my mistake. Hope that was OK :P I could tell that what I was doing was wrong by the answers on that page, but I'd like to know more about why it's wrong as I didn't fully understand.
–
cypherNov 21 '11 at 4:51

2

thats cool. a way i think of it is this それはいけない can mean "that's bad" (its often used that way) you can equate it to the american slang "don't go there" which often has nothing to do with the literal meaning but in the same way means "that's bad". a closer translation would be, we can't go there- we can't breach that topic we cant do that thing we cant cause such an infraction = thats bad それはいかない：just means i don't go but can also mean I don't want to go…行きたくないという強い意志があります。 i think its used less than the other in the figurative sense
–
yadokariNov 21 '11 at 5:06

1 Answer
1

いかない is less often a problem as it's derived from 行く, but いけない can be both the negative potential form of the verb 行く "to go" and the negative form of the verb 行ける "to be good (at)/to go well/to be acceptable." 6

Therefore いかない and いけない may appear to be similar, but they can actually be totally different.

いかない "won't go/doesn't go" from 行く:

～わけにはいかない: An expression which means "I cannot very well" when after a verb that isn't in the past tense. 5

いつまでもけんかしているわけにはいかない "I can't very well keep fighting forever." 7

いけない "unable to go/can't go" from 行く:

そのパーティーにいけない: Can mean "I can't go to the party." 2

いけない "unacceptable/bad" from 行ける5:

～てはいけない: Can mean "unacceptable if" however it's more often translated as "must not/may not." Means "must/have to" if on the end of a negative verb. 5

走{はし}ってはいけない "you must not run."

走らなくてはいけない "you must run."

～はいけない: Can mean "won't do/no good/bad" as well as "naughty."

彼{かれ}はいけない "he is naughty." 1

それはいけない "that's bad" in many contexts. 2

～て（で）いけない: Means "undesirable/unpleasant" after a conjunctive form.

いい人だが、おしゃべりでいけない "A great person, but his/her chattering isn't to be desired." 4

～といけないから… or ～といけないので… etc: On the end of verbs means "it will be bad if ~ happens so ..."

雨{あめ}が降{ふ}るといけないから傘{かさ}を持{も}ちなさい "It will be bad if it rains so take an umbrella." 1

"It's your fault that":

お前がよく[注意]{ちゅうい}していなかったのがいけないんだ "It was your fault that you weren't careful." 3

"Hopeless": (駄目{だめ}) if used as もういけない or やっぱりいけなかった.

あの病人{びょうにん}はもういけないようです "It seems that patient is beyond hope." 1

試験{しけん}はやっぱりいけなかった "Just as I feared, I've failed the exam." 1

"Unfortunate/too bad" (expressing sympathy):

それはいけません in response to hearing that someone is unwell would mean "it's unfortunate that you are unwell." 1

Other meanings:

"Beyond hope of recovery" if used as いけなくなった3

"Unable to drink alcohol" as in あまりいけない口でして4

"Darn!" when by itself, similar to しまった or ちくしょう1

Used by females as in あ、いけない、どうしよう "Oh dear, now what am I going to do?" 1